JP5513880B2 - Core cooling system - Google Patents

Description

  The present invention relates to a core cooling system, and more particularly to a core cooling system that combines a dynamic safety system and a static safety system.

  In the next-generation boiling water reactor (BWR), as a safety enhancement measure against external events such as earthquakes and tsunamis, a safety system configuration that is unlikely to fail against such external events is desired. As a proposal for this, recently, a cooling system configuration has been considered in which the accident is converged only by various devices installed in the reactor building without depending on the seawater system. For example, in a hybrid safety system of a boiling water reactor combining a dynamic safety system and a static safety system proposed in Patent Document 1, after the reactor core is submerged from outside the reactor pressure vessel (RPV), By condensing the spilled steam from the reactor pressure vessel in the heat exchanger in the cooling pool provided above the containment vessel and returning the drain water to the reactor again by gravity, the effects of dynamic equipment failure can be reduced. The structure of the cooling system which continues the core cooling eliminated as much as possible is disclosed.

The configuration of this safety system will be specifically described with reference to FIG.
In FIG. 3, the diaphragm floor 1 of the reactor containment vessel 6 is installed above the upper end of the reactor core 2, and the upper end opening of the vent pipe 5 that communicates the upper dry well 3 and the pressure suppression pool 4 is above the diaphragm floor 1. Is provided.
In addition, a static containment vessel cooling system and a pressure equalization core cooling system are provided as a safety system for long-term core decay heat removal after the loss of coolant accident.

  The static containment vessel cooling system is connected to the cooling pool 7 installed in the upper part of the reactor containment vessel 6, the heat exchanger 8 installed therein, the steam chamber 9 connected to the upper part of the heat exchanger 8, and the lower part. The water chamber 10, the steam chamber 9 and the upper dry well 3 are connected to each other, and the water chamber 10 and the upper dry well 3 are connected to each other.

  The pressure equalizing core cooling system is provided at a position lower than the upper end of the vent pipe 5 and higher than the core 2 and is composed of a pressure equalizing core cooling system pipe 14 communicating the upper dry well 3 and the reactor pressure vessel 13. .

  In the safety system thus configured, for example, when a breakage accident occurs in the primary coolant pipe as shown in 15, the outflow steam from the pipe breakage opening 15 connected to the reactor pressure vessel 13 is cooled by the static containment vessel. The vent pipe 5 is formed on the diaphragm floor 1 together with the primary cooling water that is condensed in the heat exchanger 8 constituting the system and overflows from the opening 15 of the pipe 12 and overflows from the pipe port 15 where water is poured from the outside. The reactor is accumulated through the pressure equalizing core cooling system pipe 14 by opening the pressure equalizing valves 17 and 18 which are accumulated in the open end and are installed in the main steam pipe 16 or the like to equalize the pressure in the reactor pressure vessel 13 and the upper dry well 3. Water is poured into the furnace due to a pressure difference from the pressure vessel 13 to cool the core.

JP 2009-58496 A

  In the above-described conventional safety system, the core cooling can be continuously performed only with various devices installed in the reactor building without depending on the external support system. Although strengthened, on the other hand, since a relatively large pressure equalizing core cooling system pipe is arranged in the vicinity of the upper part of the core, there is a problem that the influence of an accident when the pipe breaks becomes large.

  The present invention has been made to solve the above problems, and provides a core cooling system that can suppress the influence of an accident to a minimum even if an accident occurs in which a pressure equalizing core cooling system pipe breaks. With the goal.

The present invention has been made to solve the above problems, and a core cooling system according to the present invention includes a cooling water pool provided in an upper part of a reactor containment vessel, and a plurality of heats accommodated in the cooling water pool. An exchanger, a steam chamber connected to the upper part of each of the heat exchangers, a water chamber connected to the lower part of each, a first pipe connecting the upper dry well and the steam chambers, and the upper dryer and communicating said the wells each water chamber, a plurality of equalizing pressure furnace center that communicates with the second pipe having a riser portion of the U-shape, a nuclear reactor pressure vessel upper drywell tip having an opening a cooling pipe, said a drain pipe and the second pipe connecting the reactor pressure vessel, have a, the plurality of equalizing pressure furnace core cooling pipe is lower than the opening upper end of the vent tube at the top in its entirety from the core and said that you have been placed in.

  ADVANTAGE OF THE INVENTION According to this invention, even if the accident which a pressure equalization core cooling system piping fractures | ruptures occurs, the core cooling system which can suppress the influence of an accident to the minimum can be provided.

1 is an overall configuration diagram of a core cooling system according to a first embodiment of the present invention. The whole block diagram of the core cooling system which concerns on the 2nd Embodiment of this invention. The whole core cooling system block diagram.

  Hereinafter, an embodiment of a core cooling system according to the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is an overall configuration diagram of a core cooling system according to a first embodiment of the present invention.
Inside the reactor containment vessel 6 of the nuclear power plant, a reactor pressure vessel 13 in which the reactor core 2 is accommodated is stored, and the reactor core 2 is flooded with a reactor coolant that is reactor water. Further, an internal pump (not shown) is installed at the lower end of the reactor pressure vessel 13, and the reactor coolant is forcibly circulated through the reactor core 2.

  The reactor pressure vessel 13 is installed inside a dry well 20 composed of an upper dry well 3 and a lower dry well 19, and a pressure suppression chamber 21 is installed so as to surround the lower dry well 19 in an annular shape. The pressure suppression pool water 4 is stored inside 21. The upper dry well 3 and the pressure suppression pool water 4 are communicated with each other by a vent pipe 5, and the upper space of the pressure suppression pool water in the pressure suppression chamber 21 is the remaining non-condensation obtained by condensing the steam blown out from the vent pipe 5 at the time of the accident. Stores sex gases.

  The opening on the upper end side of the vent pipe 5 is provided so as to protrude upward from the diaphragm floor 1 which is the ceiling of the pressure suppression chamber 21, and the protruding amount is set to be higher by a predetermined length than the upper end of the core. The

  Connected to the reactor pressure vessel 13 are a main steam system 16 through which steam generated in the reactor core 2 is guided, and a water supply system 22 for supplying water after working in a steam turbine and condensed in a condenser. Is done.

  The core cooling system according to the first embodiment includes a pressure equalizing valve (DPV), an accumulating water injection system (ACC), a pressure equalizing water injection system (EPFL), a static containment vessel cooling system (PCCS), and a pressure equalizing core cooling system. Consists of Hereinafter, each safety system will be described.

(Equal pressure equalizing valve (DPV))
The pressure equalizing valve (DPV) is composed of a blast valve 17 and a remote control valve 18 installed on a pipe 23 branched from the main steam system 16 so that the reactor pressure vessel 13 and the dry well 20 can communicate with each other. After a certain period of time has elapsed, the steam is opened in the reactor pressure vessel 13 and discharged into the dry well 20 to quickly reduce the pressure in the reactor pressure vessel 13 and minimize the pressure difference with the dry well 20. . By reducing the pressure in the reactor pressure vessel 13, water can be injected by an accumulating water injection system (ACC) and an equal pressure water injection system (EPFL), and the core 2 is flooded.

(Accumulated water injection system (ACC))
The accumulator water injection system (ACC) is composed of a pressure accumulator tank 24 pressurized by nitrogen and an accumulator water injection pipe 26 connecting the pressure accumulator tank 24 and the pressure equalization water injection pipe 25. After an accident occurs, the pressure equalization valves 17, 18 In addition, water is automatically injected when the pressure in the reactor pressure vessel 13 becomes lower than the pressure in the pressure accumulating tank 24 by an automatic pressure reducing system (not shown) using a plurality of relief safety valves installed separately.

(Equal pressure water injection system (EPFL))
The pressure equalizing water injection system (EPFL) is composed of a small pump 27 that can be operated by air-cooled DG or a battery, and a pressure equalizing water injection system pipe 25 connected to the reactor pressure vessel 13 at a position above the core 2. After the pressure in the reactor pressure vessel 13 is sufficiently lowered by 18, water from the pressure suppression pool 4 is injected into the reactor pressure vessel 13 by the pump 27.

(Static containment cooling system (PCCS))
The static containment vessel cooling system (PCCS) includes a cooling pool 7 installed at the top of the containment vessel 6, a heat exchanger 8 installed therein, a steam chamber 9 connected to the top of the heat exchanger 8, and A water chamber 10 connected to the lower part, a pipe 11 communicating the upper dry well 3 and the steam chamber 9, and a water chamber 10 and the upper dry well 3 are communicated. A pipe 12 having a rising pipe portion having an opening with an open end, a drain pipe 28 communicating with the reactor pressure vessel 13 from the vicinity of the outlet of the opening, and a drain installed on the drain pipe 28 and automatically opened And an injection valve 29.

  In the event of a rupture accident in the primary coolant piping, steam is drywelled from the reactor pressure vessel 13 due to the decay heat of the core 2 even after the core 2 has been submerged by the accumulator injection system (ACC) and the equal pressure injection system (EPFL). It flows out to 20. This outflowing steam passes through the pipe 11 and is condensed in the static containment vessel cooling system heat exchanger 8 and overflows from the opening of the U-tube rising portion of the pipe 12 to the dry well.

  When the drain injection valve 29 is opened after the pressure in the reactor pressure vessel 13 is equalized with the dry well 20, the drain water accumulated in the U-shaped pipe portion is directly poured into the reactor pressure vessel 13 due to the difference in gravity, and the core. 2 is cooled. By repeating this, the decay heat of the core is removed in the long term. While steam is being discharged from the reactor pressure vessel 13, the heat exchanger 8 condenses and generates drainage. Therefore, the drain always accumulates at the rising portion of the pipe 12 and is in a sealed state.

(Equal pressure core cooling system)
The pressure equalizing core cooling system includes a pressure equalizing core cooling system pipe 14 communicating with the reactor pressure vessel 13 and the upper dry well 3 installed above the core 2 and below the upper end of the vent pipe 5 opening, and this pressure equalization. Condensate drainage water from the reactor pressure vessel 13 cooled by the containment vessel 6 wall surface and a static containment vessel, which is composed of an automatic release valve 30 and a check valve 31 installed on the core cooling system pipe 14 When drain water that flows out from the break opening when the cooling system pipe 28 is broken and drain water that overflows from the rising portion of the pipe 12 when the static containment vessel cooling system drain injection valve 29 fails to open are collected up to the diaphragm floor 1. Water is poured into the reactor pressure vessel 13 due to a difference in gravity.

  The pressure equalizing core cooling system is composed of three or more pressure equalizing core cooling system pipes 14, automatic opening valves 30 and check valves 31 provided in the respective pipes, and the pressure equalizing core cooling system pipes 14. Even when the book breaks and the valves 30 and 31 installed in the other pressure equalizing core cooling system pipe 14 fail, the remaining pressure equalizing core cooling system pipe overflows into the two dry wells. Then, the drain water and the drain water cooled by the wall of the reactor containment vessel 6 are injected into the reactor pressure vessel 13.

  In the core cooling system configured as described above, three or more containment vessel cooling system heat exchangers 8 which are static safety systems, a pipe 12 connecting the water chamber 10 and the reactor pressure vessel 13, and a drain pipe 28 are provided. When it is configured with one line per heat exchanger, the required capacity per one pressure equalizing core cooling system pipe 14 is maximized because the drain pipe 28 of the static containment vessel cooling system is broken, This is a case where the drain injection valve 29 installed in the other drain pipe 28 has failed.

  For this reason, the pressure equalizing core cooling system pipe 14 can have a diameter sufficient to allow the water injection amount of only two lines of the drain pipe 28 to flow. This corresponds to a capacity of 2/3 or less of the total drain generated in the conventional static containment vessel cooling system when water is injected through the diaphragm floor 1.

  Further, by increasing the number of heat exchangers 8 constituting the static containment vessel cooling system and the number of lines 12 and drain lines 28 to 4 and 5, the capacity of the pressure equalizing core cooling system pipe 14 is increased. It is possible to reduce the drain amount to 2/4 and 2/5. As a result, the diameter of the pressure equalizing core cooling system pipe 14 can be reduced, and the influence at the time of breakage of this system can be mitigated.

  As described above, according to the first embodiment, it is possible to reduce the pipe diameter of the pressure equalizing core cooling system pipe. Therefore, even if an accident occurs in which the pressure equalizing core cooling system pipe is broken. Therefore, it is possible to provide a core cooling system capable of minimizing the influence of an accident.

[Second Embodiment]
Next, a core cooling system according to a second embodiment of the present invention will be described with reference to FIG.
In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

In this second embodiment, instead of directly injecting drain water from the pipe 12 of the heat exchanger 8 constituting the static containment vessel cooling system (PCCS) into the reactor pressure vessel 13, the feed water pipe 22 or the pressure equalizing injection is used. A drain pipe 32 and a drain injection valve 33 are connected to the water pipe 25 or the suction or water injection pipe (not shown) of the residual heat removal system.
Thereby, after the accident occurs, the drain water is injected into the reactor pressure vessel 13 via the pressure equalizing water injection pipe 25 or the water supply pipe 22.

  According to the second embodiment, in addition to reducing the diameter of the pressure equalizing core cooling system pipe 14, the number of nozzles connected to the reactor pressure vessel 13 can be reduced, and the possibility of an accident is also reduced. Therefore, it is possible to provide a highly reliable core cooling system.

  DESCRIPTION OF SYMBOLS 1 ... Diaphragm floor, 2 ... Core, 3 ... Upper dry well, 4 ... Pressure suppression pool, 5 ... Vent pipe, 6 ... Reactor containment vessel, 7 ... Cooling water pool, 8 ... Heat exchanger, 9 ... Steam chamber, DESCRIPTION OF SYMBOLS 10 ... Water chamber, 11 ... Steam suction piping, 12 ... Piping, 13 ... Reactor pressure vessel, 14 ... Pressure equalizing core cooling system piping, 15 ... Broken part, 16 ... Main steam piping, 17 ... Pressure equalizing valve (blasting valve) , 18 ... pressure equalization valve (remote control valve), 19 ... lower dry well, 20 ... dry well, 21 ... pressure suppression chamber, 22 ... water supply piping, 23 ... piping, 24 ... pressure accumulation tank, 25 ... pressure equalizing water injection system piping, 26 DESCRIPTION OF SYMBOLS ... Accumulated water injection system piping, 27 ... Pressure equalizing water injection pump, 28 ... Drain piping, 29 ... Drain injection valve, 30 ... Automatic release valve, 31 ... Check valve, 32 ... Drain piping, 33 ... Drain injection valve.

Claims (5)

A cooling water pool provided in the upper part of the reactor containment vessel, a plurality of heat exchangers accommodated in the cooling water pool, a steam chamber connected to the upper part of each of the heat exchangers, and connected to the lower part of each a water chamber that is, a first pipe which connects the upper dry well each vapor chamber, and communicating with each water chamber and the upper drywell the riser portion of the U-shaped tip having an opening Yes a second pipe having a plurality of equalizing pressure furnace core cooling pipe which communicates the upper dry well and nuclear reactor pressure vessel, a drain pipe connecting the reactor pressure vessel and the second pipe, the And
The core cooling system more uniform pressure furnace core cooling pipe in its entirety is characterized that you have installed in the lower than the opening upper end of the vent tube above the reactor core. 2. The core cooling system according to claim 1 , wherein in each of the plurality of heat exchangers, the second pipe and the reactor pressure vessel are connected by a drain pipe .   The core cooling system according to claim 1 or 2, wherein at least three pressure equalizing core cooling system pipes are provided.   The core cooling system according to any one of claims 1 to 3, wherein a drain injection valve is provided in the drain pipe. 2. The drain pipe is connected to the second pipe and a water supply pipe of a reactor pressure vessel, or is connected to a pressure equalizing water system pipe of the second pipe and a reactor pressure vessel. to 4 reactor core cooling system according to any one.

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